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Input Signals
-Clear to Send:
(-CTS), Pin 36-The
I
-CTS
I
signal is a
modem-control function input, the condition of which can be
tested by the processor by reading bit 4 (CTS) of the modem
status register. Bit 0 (DCTS) of the modem status register
indicates if the
I
-CTS
I
input has changed state since the previous
reading.
Note: Whenever the CTS bit of the modem status register
changes state, an interrupt is generated if the modem-status
interrupt is enabled.
-Data Set Ready:
(-DSR), Pin 37-When low, indicates the
modem or data set is ready to establish the communications link
and transfer data with the controller. The '-DSR
I
signal is a
modem-control function input, the condition of which can be
tested by the processor reading bit 5 (DSR) of the modem status
register. Bit 1 (DDSR) of the modem status register indicates if
the
I -
DSR
I
input has changed since the previous reading.
Note: Whenever the DSR bit of the modem status register
changes state, an interrupt is generated if the modem-status
interrupt is enabled.
-Data Carrier Detect:
(-DCD), Pin 38-When low, indicates
the modem or data set detected a data carrier. The
I
-DCD
I
signal is a modem-control function input, the condition of which
can be tested by the processor reading bit 7 (DCD) of the modem
status register. Bit 3 (DCD) of the modem status register
indicates if the
I -
DCD
I
input has changed state since the
previous reading.
Note: Whenever the DCD bit of the modem status register
changes state, an interrupt is generated if the modem status
interrupt is enabled.
- Ring Indicator: (-
RI), Pin 39-When low, indicates the modem
or data set detected a telephone ringing signal. The
I -
RI
I
signal
is a modem-control function input, the condition of which can be
4 Serial/Parallel Adapter
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